Refrigerating systems



Jan. 12, 1965 J. E. WATKINS REFRIGERATING SYSTEMS 2 Sheets-Sheet 1 Filed March 28, 1963 INVENTOR. WATKINS Jon-1N E.

ATTYS.

Jan. 12, 1965 J. E. WATKINS 3,164,973

REFRIGERATING SYSTEMS Filed March 28, 1965 2 Sheets-Sheet 2 INVENTOR. JOHN E, WATKlNS BY Wo 7W, Vabf% ATTYS,

United States Patent D 3,164,973 REFRIGERATlNG SYSTEMS John E; Watkins, 1311 S. 4th Ave, Maywood, Ill. Fiied Mar. 28, 1963, Ser. No. $8,695 6 Claims. (Cl. 625G9) The present invention relates to improvements in refrigerating systems such as disclosed in my prior Patent No. 2,590,741. This prior patent sets forth a system wherein evaporators of the refrigerating system are continuously operated in a flooded condition withliquid refrigerant overfeed passing through the evaporators being periodically returned and recirculated to the system.

Because the recirculated liquid refrigerant overfeed has a sharply lower temperature at suction pressure than the liquid refrigerant from the system condenser, where the overfeed is fed directly to the liquid line to the evaporator coils, this liquid line is alternately subjected to frosting during the periods of cold liquid refrigerant overfeed recirculation and thawing during periods of warm liquid refrigerant feed from the system condenser. The main object of the present invention is to recirculate liquid refrigerant overfeed to the evaporator coils without setting up water condensation on the liquid line and drippage resulting therefrom because of the alternate frosting and thawing of an uninsulated liquid feed line without valve means between the condenser and receiver as disclosed in the recirculating means of my prior patent.

A further object is to eliminate liquid line drippageby raising the temperature of the recirculated liquid refrigerant using heat from within the refrigerating cycle.

A related object is to raise the temperature of the recirculated liquid while holding refrigeration loss to a minimum and in a direct manner requiring the least expensive mechanism.

Other objects will appear from the following description taken in connection with the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic view of a refrigerating system embodying the features of the invention;

FIG. 2 is a diagrammatic View of a system employing an alternative liquid overfeed heating means; and

FIG. 3 is a fragmentary diagrammatic view of a pumper tank with further alternative liquid overfeed heating means.

While the invention is susceptible to various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail certain preferred embodiments, and it is to be understood that I do not thereby intend to limit the invention to the specific forms disclosed, but do intend to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.

For purposes of illustration the invention has been shown as embodied in a refrigerating system as shown and described in hereinbefore mentioned Patent No. 2,590,741 in which a liquid refrigerant, such as ammonia, is supplied from a common source to a plurality of evaporators in the form of cooling coils It). The cooling coils, of which there may be more than one shown, may be located in different rooms of a cold storage plant or in different cooling units of the installation, in accordance with conventional practice.

The source of liquid refrigerant may be of any preferred type and as herein shown comprises a compressor 11, a condenser 12 into which the compressor discharges, and a receiver 13 for storing the liquid refrigerant pro duced in the condenser. The foregoing elements may all be of conventional construction. Liquid refrigerant from the receiver13 is supplied by way of a feed line 14 to the cooling coils 19, each of which has its inlet end when Patented Jan. 12, 1965 connected with the feed line and outlet end connected by a common suction line 15 with the suction side of the compressor 11.

While in the system which is illustrated, it is contemplated that control of liquid flow through the coils 10 may be effected by simple orifice means 16 to provide deliberate liquid overfeed, it will be understood that this is exemplary only, and the present invention is applicable to other types of systems where liquid in the suction side of the system may be trapped and recirculated.

In the system shown in FIGURE 1 of the drawings, any excess liquid passing through the cooling coils is trapped in a surge tank or accumulator 17 connected in the suction line 15. To recirculate or return the excess liquid refrigerant to the system, provision is made for draining the trapped liquid to an auxiliary accumulator or pumper tank 19. For this purpose, the auxiliary accumulator or pumper tank 19, herein shown as comprising a cylindrical sheet metal tank, is connected with the main accumulator 17 by a conduit 20 which opens into the latter adjacent its upper end. A valve V is interposed in the conduit 20 for closing it when the auxiliary accumulator is to be emptied, as will be described hereinafter. The valve V shown is of the open and closed type, but if sufficient head of liquid is available a check valve may be used instead to permit drainage of the liquid from the main accumulator to the auxiliary accumulator while preventing reverse fiow through the conduit 29.

A vent conduit 21 opening from the upper end of the pumper tank 19 and connected with the suction side of the system serves to equalize the pressure in the two accumulators and thus permit gravity flow of liquid through the conduit 20. A valve V1 in the conduit 21 controls this vent connection.

For conducting the collected liquid to the liquid line connected to the evaporator coils, the pumper tank 19 is connected by a conduit 23 with the feed line 14. During the discharge of liquid, the feed line is closed off from the source of liquid refrigerant by a valve V2 interposed in the line between itsjunction with the conduit 23 and the liquid refrigerant source. A check valve CV is interposed in the conduit 23 to prevent flow of refrigerant from the feed line into the pumper tank while permitting flow to the line.

In accordance with one of the main features of the present invention, the liquid collected in the pumper tank,

which is at suction temperature having passed through the evaporator coils, is heated prior to being conveyed through the liquid feed line to the evaporator coils so as to raise the temperature of the liquid overfeed refrigerant and thereby avoid condensation on the liquid line resulting in unwanted water drippage. In keeping with a preferred embodiment of the invention, the liquid refrigerant is heated while in the pumper tank 19 and before being expelled into the liquid line, by heat derived from within the refrigerating cycle. To this end, a conduit 24 connected to the top of the receiver 13 and having an outlet 25 at the bottom of the pumper tank 19 conveys gas at receiver pressure and temperature to the bottom of the pumper tank 19 and bubbles the gas into the liquid collected therein. A perforated plate 26 fixed in the pumper tank above the gas entry point distributes the gas throughout the liquid. With this arrangement, the gas will condense, giving oif heat which will tend to raise the temperature of the liquid in the pumper tank 19. If the process is continued, the gas and liquid in the tank 19 will become saturated and the saturated liquid raised to the temperature of the gasfrom the receiver. A solenoid valve V3 in the saturating gas line 24 is operated to regulate periodic supply of refrigerant gas to the pumper tank.

It is one of the features of the present invention that line condensation is minimized.

. temperature and fed into the line.

the gas which is supplied from the receiver 13 to the pumper tank 19 provides the energy for expelling the liquid in the tank into the liquid line as well as raising the temperature of the liquid in the pumper tank to the desired point.

To hold refrigeration loss to a minimum, the liquid warm-up should be stopped as soon as the required temperature is reached. Otherwise, as the condensing pressure increases with oncoming warm weather, the gas conveyed therefrom to the pumper tank will warm the liquid therein to higher temperatures than are necessary for Water drippage prevention. In keeping with a further feature of the invention, a gas by-pass solenoid valve V4 is provided which is operable from the pressure in the receiver and, therefore, in the pumper tank 19 being raised to a predetermined pressure level.

For operating the gas by-pass solenoid valve V4, a pressure switch P1 is connected to the pumper tank to be responsive to the pressure therein, and is set to trip at the pressure corresponding to the desired warm-up limit temperature. For example, the pressure switch Pi may be set to trip at 70 p.s.i. gage, which corresponds for ammonia to 47 F., the latter being high enough that pipe The pressure switch P1 is effective to shift the system to the return cycle by closing solenoid valve V2 at the receiver, closing solenoid V3 of the saturating gas line, and opening the by-pass solenoid valve V4, as indicated by the broken line connections with P1 in the drawings. With such an arrangement, the pressure switch P1 is effective through the control system to automatically shift and time the return cycle, whereby liquid overfeed at low temperature is heated to a desired On systems susceptible to wide fluctuations in condensing pressure, switch P1 may be a differential switch set to trip at a set differential pressure below the condensing or receiver pressure.

The time required for heating the liquid overfeed will depend upon factors such as the rate at which warm gas is supplied from the receiver to the pumping tank; and as will be apparent to one skilled in the art, such factors may be taken into account when constructing a system.

An exemplary apparatus embodiment of the present invention, shown in FIGURE 1, comprises an ammonia plant of 100 tons capacity operating at 10 p.s.i. gage suction pressure and 80 p.s.i. gage condensing (receiver) pressure. In this system, the liquid ammonia supplied from the pumping tank I? through the liquid line 14 is at 10 p.s.i. gage or -8.4 P, such that substantial water drippage may be expected from the liquid line 14 if, during the return cycle, liquid refrigerant at the low 8.4

F. suction temperature is fed into the line from the pumper tank 19. It is assumed, for this example, that if during the return cycle liquid ammonia from the pumper tank is maintained at 70 p.s.i. gage (about 47 F.) the liquid line 14 will not drip.

According to the preferred apparatus embodiment of the invention, therefore, the liquid refrigerant in the pumper tank 19 is heated from 8.4 F. to about 47 F. and then supplied to the evaporator coils 16 through the liquid line 14. To warm the liquid refrigerant in the pumper tank 1%, which in this example holds 87.2 lbs. of liquid ammonia, will require 5330 Btu. Warm vapor from the receiver 13 at 80 p.s.i. gage saturated gives up 531 B.t.u. per pound when condensed at 47 F. To provide the Warm-up with warm vapor will require approximately 5330+53l=l0 lbs. receiver; 52.5 cubic feet of vapor at receiver pressure is Vapor introduced from the required to be introduced from the receiver. If, in this example, a return cycle is effected every ten minutes, it would be suitable to provide a threeor four-minute Warm-up period. The required vapor can readily be introduced through a. line 24 connecting the receiver 13 with the pumper tank 19. Volume is provided in the pumper tank for the accumulation of the warming vapor as it condenses, to prevent any premature hydrostatic action on switch Pl.

While in the apparatus embodiment of FIGURE 1 the liquid overfeed has been heated by hot gas from the system, other methods may be used for supplying the requisite heat to the cold liquid refrigerant. For example, as shown in P16. 2. liquid refrigerant from the receiver 3 at condensing pressure and temperature (ie, St) p.s.i. gage, 53 1 may be mixed in a mixing tank 3t; with liquid refrigerant overfeed from the pumper tank 9 at suction pressure and temperature (i.e., l0 p.s.i. gage, 8.4 F.), resulting in liquid refrigerant at an intermediate temperature high enough to substantially reduce water drippage supplied through the liquid line id. In this form of the invention, Warm gas from the receiver 23 is introduced to the pumper tank l9 above the liquid therein so as to provide energy for expelling the liquid from the pumper tank l into the mixing tank 39. One feature of this arrangement is that the return cycle may be started without delay while arriving a liquid tei perature high enough for satisfactory operation.

As a further arrangement for heating the liquid overfeed, it has been found suitable, as shown in FIG. 3, to employ heating coils 32. which are located within the pumper tank 1) and supplied from a source of warm gas or warm liquid. Such coils may, if desired, be in the form of electrical heating elements. In this arrangement, gas at receiver temperature and pressure is supplied to the pumper tank 1? above the liquid therein and furnishes energy for expelling the heated liquid. While this arrangement can be operated to supply liquid at requisite temperature to avoid liquid line water drippage, there will be a reduction in overall system efficiency due to the introduction of heat derived from outside the system.

In the examples given above, the pressure within the receiver was specified as 80 psi. gage. In keeping with one of the features of the refrigeration system which is disclosed herein, condenser temperature and pressure is allowed to rise and fall seasonably according to the temperature of the cooling medium, usually air or water, circulated over the condenser coils. The temperature of the refrigerant circulated through the condenser coils, therefore, will vary from low winter temperatures to "iigher summer temperature, resulting in variations in the temperature and pressure of liquid refrigerant collected in the receiver. By operating the evaporator coils so as to have liquid overfe-ed under all condenser (and receiver) pressure and temperature conditions, relatively simple expansion valves at a fixed setting may be used. Higher system efilClEl'lCY is provided by collecting the liquid overfeed from the suction line in the auxiliary accumulator and recirculating such liquid through the evaporator coils. It will be observed, however, that the temperature of the liquid overfeed will also vary; however, under all conditions its temperature will be substantially lower than the temperature of the liquid refrigerant available from the receiver.

I claim as my invention:

1. In a refrigerating system, a source of liquid refrigerant at one pressure and temperature, an evaporator coil, a liquid line connected to feed liquid refrigerant from said source of said coil, means in said line adjacent said coil to expand liquid refrigerant from said source to substantially lower temperature and pressure with cold liquid overfeed passing through said coil, means for collecting said cold liquid overfeed, and means associated with said collecting means for heating said cold liquid overfeed and for returning warm liquid overfeed in said collecting means from said collecting means to said coil through said liquid line.

2. In a refrigerating system, a source of liquid refrigerant at one pressure and. temperature, an evaporator coil, a liquid line connected to feed liquid refrigerant from said source to said coil, means in said line adjacent said coil to expand liquid refrigerant from said source to substantially lower temperature and pressure with liquid overfeed passing through said coil, means for collecting said liquid overfeed, means associated with said collecting means for heating said liquid overfeed, and means responsive to said cold liquid overfeed attaining a predetermined temperature for returning warmed liquid overfeed from said collecting means to said coil tmough said liquid line.

3. In a refrigerating system, a source of refrigerant including means for compressing refrigerant gas and means for condensing refrigerant gas to liquid, an evaporator coil, a liquid line connected to feed liquid refrigerant from said source to said coil, means in said line adjacent said coil to expand said liquid refrigerant to substantially lower temperature and pressure with liquid overfeed passing through said coil, means including a tank for collecting said liquid overfeed, means for conveying refrigerant gas from said source to said tank and for passing said gas through liquid overfeed therein so as to heat said liquid overfeed, and means for returning warmed liquid overfeed from said tank to said coil through said liquid line.

4. In a refrigerating system, a receiver for refrigerant at receiver pressure and temperature, an evaporator coil, a liquid line connected to feed liquid refrigerant from said receiver to said coil, means in said line adjacent said coil to expand liquid refrigerant from said receiver to substantially lower temperature and pressure with saturated liquid overfeed passing through said coil, means including a tank for collecting said liquid overfeed, means for conveying refrigerant gas from said receiver to said tank and for passing said gas through liquid over-feed therein so as to heat said liquid overfeed, other means for conveying refrigerant gas from said receiver to said tank above liquid therein so as to provide pressure for expelling said liquid overfeed from said tank, and means for conducting expelled warmed liquid overfeed from said tank to said coil through said liquid line.

5. In a refrigerating system, a source of liquid refrigerant at one pressure and temperature, an evaporator coil, a liquid line connected to feed liquid refrigerant from said source to said coil, means in said line adjacent said coil to expand liquid refrigerant from said source to substantially lower temperature and pressure with liquid overfeed passing through said coil, means including a tank for collecting said liquid overfeed, a heating element in said tank for heating said liquid overfeed, and means for returning warmed liquid overfeed to said coil through said liquid line.

6. In a refrigerating system, a source of refrigerant including means for compressing refrigerant gas and means for condensing refrigerant gas to liquid, an evaporator coil, a liquid line connected to feed liquid refrigerant from said source to said coil, means in said line for sun plying said liquid refrigerant from said source to said coil in an amount greater than the coil is capable of evaporating, means including a tank for collecting the liquid overfeed from said coil, means for conveying refrigerant gas from said source to said tank and for passing said gas through the liquid overfeed therein so as to heat said liquid overfeed, means for conveying refrigerant gas from said source to said tank above the liquid therein so as to provide pressure for expelling said liquid overfeed from said tank, and means for conducting the expelled warmed liquid overfeed from said tank to said coil.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Bulletin R-3, page 2, J. E. Watkins Company, 1311 S. 4th Ave., Maywood, Ill. 

1. IN A REFIGERATING SYSTEM, A SOURCE OF LIQUID REFRIGERANT AT ONE PRESSURE AND TEMPERATURE, AN EVAPORATOR COIL, A LIQUID LINE CONNECTED TO FEED LIQUID REFRIGERANT FROM SAID SOURCE OF SAID COIL, MEANS IN SAID LINE ADJACENT SAID COIL TO EXPAND LIQUID REFRIGERANT FROM SAID SOURCE TO SUBSTANTIALLY LOWER TEMPERATURE AND PRESSUER WITH COLD LIQUID OVERFEED PASSING THROUGH SAID COIL, MEANS FOR COLLECTING SAID COLD LIQUID OVERFEED, AND MEANS ASSOCIATED WITH SAID COLLECTING MEANS FOR HEATING SAID COLD LIQUID OVERFEED AND FOR RETURNING WARM LIQUID OVERFEED IN SAID COLLECTING MEANS FROM SAID COLLECTING MEANS TO SAID COIL THROUGH SAID LIQUID LINE. 